The present invention relates to improvements in a controlled deflection roll of the type wherein a pressure roll shell is rotatably carried on a stationary shaft and supported by a fluid pressure chamber between the roll shell and shaft so that the roll shell is carried on a chamber of fluid, and its working force is transmitted through the fluid to the shaft.
More particularly, the invention relates to improvements in a structure and method for pressurizing the pressure chamber between the roll shell and shaft. In structures of the type heretofore used such as disclosed in U.S. Pat. No. 2,908,964 Appenzeller and successive modifications of the concept shown therein, the pressure chamber between the roll shell and shaft was pressurized by a pump which pumped a fluid such as oil into the pressure chamber. In accordance with the concept of this type of roll, the roll shell engages another roll along the working face to form a pressure nip. The nip is kept essentially straight by pressurizing the chamber between the shaft and shell with pumped oil, and the forces in the nip are transmitted from the roll shell through the fluid to the shaft so that the shaft bends, but the roll shell sees only the hydrualic pressure of the fluid and is maintained essentially straight.
This type of construction requires the provision of an oil pump with accurate control mechanism to control the pressurization in the chamber. Further, pressure must be present in the chamber at start-up to avoid abrasion and scoring the inner surface of the roll shell against the shaft, and the pressure in the chamber must be maintained at a predetermined pressure in accordance with the nip pressure needed for the pressing operation. Seals are provided to prevent leakage from the pressure chamber and this has heretofore been the sole function of such seals. Leakage past the seals had to be compensated for by delivery of oil to the pressure chamber. Since the nip pressure was determined wholly by the pressure in the chamber, accurate control of the pressure and of the pump had to be maintained and erratic behavior such as pump pulsations or pump failure could not be countenanced. Also, the capacity of the pump had to be sufficient to compensate for the leakage past the seals and to be sufficient to deliver sufficient fluid for operation under maximum nip pressure conditions. Since the roll often was called upon to operate in either direction, the seals had to be designed so that they could accommodate rotation in either direction without substantial change in leakage.
It is an object of the present invention to provide an improved controlled deflection roll which eliminates the necessity for a controlled pressure pump to pressurize the chamber in a controlled pressure roll.
A further object of the invention is to provide an improved method and apparatus whereby the roll is self-loading and self-pressurizing so that the working pressure in the chamber will automatically be provided with rotation of the roll and so that operation of a pressure pump does not have to be coordinated with operational speeds and pressures of the roll shell.
A general object of the invention is to provide an improved roll shell construction which is capable of maintaining a more uniform nip pressure and operating more reliably so as to avoid accidental damage to the roll shell and shaft with equipment failure and which is capable of continued long term operation with improvements over structures and methods heretofore available.
A feature of the invention is to provide a controlled deflection roll embodying a roll shell carried on a stationary shaft with a pressure chamber between the shaft and shell for carrying the shell wherein the chamber is pressurized by fluid induced to move past the seal at the oncoming side of the pressure chamber due to movement of the inner surface of the roll shell past the seal and a pressure relief passage is provided to relieve excess pressure within the chamber and maintain the chamber at a constant desired pressure.
A further object of the invention is to provide an improved seal for a controlled deflection roll so that the roll is self-energizing eliminating the need for a pump to create lubrication pressure, wherein the design has fewer parts and is more cost effective than that heretofore available in the prior art, and wherein the seal allows lubrication pressure to develop in both directions of rotation.